In the ovary, ERα is the predominant ER isotype in theca and interstitial cells (Schomberg et al., 1999), ERα null females exhibit large, hemorrhagic and cystic follicles and infertility (Couse and Korach, 1999; Couse et al., 2003; Emmen and Korach, 2003). This evidence concerns the gene ESR1 and Infertility.